Effect of Vacuum Annealing Temperature on the Binary System Ni/Si(100)

Metal silicide films are widely applied in microelectronic industry, they have been used as rectifier and ohmic contacts. Most of metals react with silicon to form silicide, the deposition of a thin metal layer is obtained by different techniques. The common methods are vacuum evaporation with filament or e-gun, sputtering, and chemical vapor deposition. The vacuum deposition of a thin layer of metal on a silicon substrate is one of the most widely used. The metal silicide film is grown on a silicon substrate and then annealed at different thermal budgets. In this work, to prepare a silicide film, we have used as a technique vacuum evaporation PVD (physical vapor deposition) by using a nickel (Ni) filament with high purity. On a substrate of naturally oxidized Si(100) and after HF surface preparation, two layers of nickel are deposited, namely of 56 nm and 35 nm. These different samples (Ni(56 nm)/Si(100) and Ni(35 nm)/Si(100)) were then vacuum annealed at different thermal budgets and at temperatures equal to 350, 500, 650 and 750 °C for a time equal to 30 min. The characterization of the obtained layers was made by the following techniques: X-ray diffraction (XRD) for studying the structure of the films (phase identification), the four-point probe technique for measuring the sheet resistance of the phase(s), and the surface roughness study was carried out using atomic force microscopy (AFM). The growth of Ni on naturally oxidized Si(100) substrates has been studied by different techniques which confirmed that the vacuum annealing temperature has a very important effect, NiSi monosilicide phase appears from 650 °C. The morphology analysis of the interface revealed the presence of different phases NiSi, NiO and Ni2O3 which is confirmed by structural analysis. Also, good coherence was observed between XRD results with those of the sheet resistance and the RMS surface roughness measurements.